Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Year 2 Loco > 18. Muscle in health and disease - Robson > Flashcards

18. Muscle in health and disease - Robson Flashcards

1
Q

What is the pattern of nuclei in a skeletal muscle cell?

A

Multinucleate cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Where are the nuclei located in cells of skeletal muscle?

A

Nuclei are positioned peripherally

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How long are skeletal muscle fibres?

A

10cm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the diameter of skeletal muscle fibres?

A

Vary between 10-100 micrometers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the significance of centrally located nuclei in skeletal muscle fibres?

A

Satellite cells have been activated to repair damaged muscle (nucleus moves back into the periphery once repaired)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the endomysium?

A

Aereolar connective tissue - covers each muscle fibre/muscle cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the perimysium?

A

Connective tissue sheath - surrounds a bundle of muscle fibres from 10-100 - forms a muscle fascicle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the epimysium?

A

Fibroelastic tissue surrounding a muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How many muscle fibres are contained within a muscle fascicle?

A

Between 10-100

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the centre of a skeletal muscle cell composed of?

A

Nuclei are peripheral so the centre is full of actin and myosin contractile proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Is skeletal muscle striated muscle? Why?

A

Yes - sometimes called striated muscle

This is because the actin and myosin form streaks - striated appearance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the shape of nuclei in the periphery of skeletal muscle cells?

A

Flattened

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the shape of nuclei in the centre of skeletal muscle cells?

A

More rounded and bigger

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is skeletal muscle innervated by?

What does the innervation of the skeletal muscle lead to?

A

Innervated by motor neurones - initiate the contraction of the muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What chemical is involved in the innervation of skeletal muscle and where are these released from?

What are the receptors involved with this?

A

Ach

Ach released from the synapse terminal
Activation of nicotinic Ach receptor on the muscle fibre
Muscle contraction is initiated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How many muscle fibres are innervated by one motor neurone?

A

Between 5-200 muscle fibres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is a motor unit?

A

These are the 5-200 muscle fibres that are all innervated by the same action potential from the same motor neurone - these fibres all contract at the same time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the significance of the loss of a single motor neurone?

A

Then all the muscle fibres that are innervated by this motor neurone will cease to function - i.e. the whole motor unit will cease to function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the effect on the shape of the skeletal muscle fibre if there is a loss of the innervating motor neurone?

A

Loss of innervating motor neurone
Muscle fibres are no longer innervated - become deinnervated and are no longer used
These muscle fibres undergo atrophy and become angulated in shape

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the process of reinnervation?

A

Deinnervated muscle fibres - start to atrophy and releases stress signals to neighbouring muscle fibres (at the neuromuscular junction)
Causes neighbouring motor neurones to sprout extra ends to innervated these deinnervated muscle fibres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Where are stress signals from deinnervated muscle fibres sent to?

A

Neuromuscular junction of neighbouring muscle fibres - want to signal to the motor neurone innervated neighbouring motor unit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the main consequence of reinnervation?

A

More muscle fibres are being innervated by the same motor neurone - the size of the motor unit is increasing
Fibres are now more grouped together
Results in switch in the phenotype of the neighbouring muscle fibres and hence alters proper functioning of the muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the phenotype of a muscle fibre dependent on?

A

Dependent on the frequency of stimulation of the motor unit by the motor neurone
The frequency influences whether you have fast or slow twitch fibres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How does reinnervtion result in a switch in the phenotype of muscle fibres?

A

If fibres from slow frequency motor neurones die and are now innervated by fibres from high frequency motor neurones - these fibres will switch in the phenotype

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is the common name given to infantile hypotonia?

A

Floppy baby syndrome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What are the two different types of infantile hypotonia?

A

One affecting type 1 muscle fibres

One affecting type 2 muscle fibres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What type of metabolism is undergone by type 1 muscle fibres?

A

Mainly aerobic metabolism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What type of metabolism is undergone by type 2 muscle fibres?

A

Mix of aerobic and anaerobic metabolism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What are the two different types of infantile hypotonia and how do these present differently?

A

One - hypertrophy of the type 1 muscle fibres and disproportion between the size of the muscle fibres
Two - hypertrophy of the type 2 muscle fibres and disproportion between the size of the muscle fibres

The phenotype between these two is actually the same

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Are type 1 muscle fibres slow or fast contracting?

A

Slow contracting/slow twitch

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Are type 2 muscle fibres slow or fast contracting?

A

Fast contracting/fast twitch

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

How can you distinguish between the two types of infantile hypotonia?

A

Using an ATP scan and looking at the ATP levels being used for contraction of the fibre

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Can a H&E scan be used to distinguish between the two types of infantile hypotonia?

A

No

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

When does infantile hypotonia arise?

A

Congenital

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What is the effect of infantile hypotonia on the individual in later life?

A

Individual can undertake normal daily activity and live normal lives but cannot do such intense sports and they get tired a lot faster

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Does the hypotonia in infantile hypotonia improve in later life?

Why?

A

Fibres start to improve as the infant gets older - there is a lot of continued growth of the muscle postnatally

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Do type 1 muscle fibres appear pale or dark?

A

Pale

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Do type 2 muscle fibres appear pale or dark?

A

Dark

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

What is sarcopenia?

A

The loss of skeletal muscle strength and mass as a result of ageing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What conditions is sarcopenia closely associated with?

A

Osteoporosis

41
Q

Do individuals experience weight loss when they have sarcopenia? Why?

A

No.

Because the muscle that is lost is replaced with fat

42
Q

What is the difference in the onset in sarcopenia between men and women?

A

There is no difference

43
Q

Give some potential cases for sarcopenia

A

Loss of motor neurones with age
Suboptimal nutrition
Mitochondrial dysfunction associated with ageing
Chachexia

44
Q

What is chachexia?

A

Increase in the number of inflammatory conditions whilst we age - release of proinflammatory cytokines which cause damage to muscle

45
Q

What are the three stages involved in diagnosing muscle disorders?

A

History
Muscle biopsy
Needly EMC

46
Q

What is involved in taking a history to diagnose a muscle disorder?

A 
Pain and weakness in the muscle
Twitching and cramps 
Muscle atrophy and contractures 
Family history 
Any endocrine disorders?
47
Q

What is the purpose of the needle EMC in diagnosing a muscle disorder?

A

Use this to differentiate between a neuropathy and a myopathy

48
Q

What is a neuropathy?

A

Disease or dysfunction of one or more peripheral nerves

49
Q

What is a myopathy?

A

Disease of muscle tissue/muscle membrane - spontaneously activated

50
Q

What are the different types of myopathies?

A

Inflammatory

Degenerative

51
Q

What are inflammatory myopathies commonly associated with?

A

Microbial infections

52
Q

Which muscles are affected first in inflammatory myopathies?

A

Proximal muscles - big muscles of the shoulder and the hips, arms and thighs - symmetrical involvement

53
Q

Give the name of two types of inflammatory myopathies

A

Polymyositis

Dermatomyositis

54
Q

Are inflammatory myopathies autoimmune conditions?

A

Yes

55
Q

Are inflammatory myopathies more prevalent in males or females?

A

Females

2:1 ratio

56
Q

What is the common age of onset of inflammatory myopathies?

A

40-60 years

57
Q

What is indicated by a raised serum creatinine kinase level?

A

Indicates that muscle fibres have been injured - these are releasing creatinine kinase into the blood

58
Q

What will an EMG trace look like if there is no muscle movement?

A

Trace will be flat

59
Q

What is the most definitive investigation for an inflammatory myopathy?

A

Biopsy

60
Q

What can be looked for in a muscle biopsy?

A

Variation in fibre size
Central nuclei
Necrosis and regeneration
Infiltrate of inflammatory cells (lymphocytes)

61
Q

What is the typical clinical presentation of dermatomyositis?

A

Purple coloured rash over the eyelids - the forehead is spared
May have a stripy appearance on the back

62
Q

What is calcification at the dermis indicative of?

A

Involvement of the skin in an inflammatory myopathy - autoimmune condition

63
Q

What autoimmune antibodies are prevalent in inflammatory myopathies?

A

ANA - antinuclear antigens e.g. anti-Jo1 in fibroblasts

64
Q

What is the treatment for inflammatory myopathies?

A

Corticosteroids - high dose until creatinine kinase levels return to normal
Infliximab (t-cells) and rutuximab (b-cells)

65
Q

What is the problem with stopping the corticosteroids too early when treating inflammatory myopathies?

A

If you stop too early - can end up with a flare of the disease which is even harder to control

66
Q

What is the most common cause of death in individuals with inflammatory myopathies?

A

Pulmonary fibrosis - the connective tissue of the lungs becomes inflamed

67
Q

What is inclusion body myositis?

A

This is a common muscle disease of the elderly

Only small muscle groups are involved

68
Q

Is inclusion body myositis more common in males or females?

A

Males

69
Q

Why is dysphagia common in inclusion body myositis (BM)?

A

The muscles in the oesophagus can be affected

70
Q

How does inclusion body myositis appear on a biopsy?

A

Presence of inclusions and muscle damage

71
Q

What are ‘inclusions’?

A

These are proteins that are abnormally folded

These form complexes known as vacuoles - these should not be present in muscle as they can cause damage

72
Q

What protein is commonly involved in the formation of inclusions and vacuoles in IBM?

A

Beta-amyloid and hyperphophorylated Tau

73
Q

What neurological condition is IBM very similar to?

A

Alzheimer’s disease - but in the muscle

74
Q

What is a muscular dystrophy?

A

A hereditary condition marked by progressive weakening and wasting of the muscles

75
Q

What is Duchenne muscular dystrophy?

A

Severe muscular dystrophy caused by genetic defect - severe weakening of the muscles
X-linked so seen in boys

76
Q

What is Becker’s muscular dystrophy?

A

This is a milder form of Duchenne muscular dystrophy

77
Q

Which muscles are mainly affected in muscular dystrophies?

A

The big, proximal muscles

78
Q

Are the female carriers of Duchenne muscular dystrophy symptomless?

A

No - have a milder form

79
Q

What are the creatine kinase levels like in an individual with Duchenne muscular dystrophy?

A

Elevated - muscle damage

80
Q

What is the prognosis of Duchenne muscular dystrophy?

A

Continuous slow decline
Cannot walk by 7-12 years
Death in mid-late teens but now in late 20s to early 30s

81
Q

What are the three characteristics seen in a biopsy in Duchenne muscular dystrophy?

A

Muscle fibres undergoing phagocytosis
Centrally located nuclei
Variation in the size of the muscle fibres

82
Q

What happens in Duchenne muscular dystrophy?

A

There is a loss of muscle - muscle fibres undergo phagocytosis and are damaged - centrally located nuclei appear
Muscle is then replaced by fibrous tissue - either connective tissue or fat
Muscles are weakened

83
Q

Why do many individuals with Duchenne muscular dystrophy commonly die from cardiac complications?

A

Cardiac muscle does not have satellite cells and so it cannot repair itself

84
Q

What type of myopathy can occur from corticosteroid intake?

A

Type 2 fibre atrophy

85
Q

What type of myopathy can occur from alcohol intake?

A

Type 2 fibre atrophy

86
Q

What is rhabdomyolosis?

A

The destruction of striated muscle cells

87
Q

What is fibromyalgia?

A

Widespread muscle pain - problem of the connective tissue around the muscle

88
Q

Is fibromyalgia more common in males or females?

A

80-90% of patients are female

89
Q

In what age group is fibromyalgia common?

A

30-60 year olds

90
Q

What is the common treatment for fibromyalgia?

A

Amitriptyline antidepressant - neuropathic pain analgesic
Also helps to reset the normal sleep cycle

Also SSRIs and exercise

91
Q

Polymyositis and dermatomyositis are what type of muscular condition?

A

Inflammatory myopathy

92
Q

Main cells involved in inflammatory myopathies are?

A

Lymphocytes

93
Q

Dysphagia is a sign of what muscular condition?

A

Inclusion body myositis - damage to oesophagus

94
Q

Muscle composition of the oesophagus is?

A

Upper 1/3 - striated/skeletal muscle
Lower 1/3 - smooth muscle

Middle - transitional

95
Q

What reflex is lost in inclusion body myositis?

A

Quadriceps reflex - associated polyneuropathy

96
Q

Is creatinine kinase raised in IBM?

A

Mildly

97
Q

Duschenne muscular dystrophy occurs in males or females?

A

Males - x-linked

98
Q

Rhambdomyelosis is caused by intake of what drug type?

A

Statins

Year 2 Loco (31 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions